1. Field of the Invention
Aspects of the present invention generally relate to wireless communication systems. More particularly, embodiments of the present invention relate to a wireless communication system that provides telephone, data and Internet connectivity to a plurality of users.
2. Description of Related Art
Several systems are currently in place for connecting computer users to one another and to the Internet. For example, many companies such as Cisco Systems, provide data routers that route data from personal computers and computer networks to the Internet along conventional twisted pair wires and fiber optic lines. These same systems are also used to connect separate offices together in a wide area data network.
However, these systems suffer significant disadvantages because of the time and expense required to lay high capacity communications cables between each office. This process is time consuming and expensive. What is needed in the art is a high capacity system that provides data links between offices, but does not require expensive communication cables to be installed.
Many types of current wireless communication systems facilitate two-way communication between a plurality of subscriber radio stations or subscriber units (either fixed or portable) and a fixed network infrastructure. Exemplary systems include mobile cellular telephone systems, personal communication systems (PCS), and cordless telephones. The objective of these wireless communication systems is to provide communication channels on demand between the subscriber units and the base station in order to connect the subscriber unit user with the fixed network infrastructure (usually a wired-line system). Several types of systems currently exist for wirelessly transferring data between two sites. For example, prior art wireless communication systems have typically used a Code Division Multiple Access (CDMA), Time Division Multiple Access (TDMA) or Frequency Division Multiple Access (FDMA) type system to facilitate the exchange of information between two users. These access schemes are well known in the art.
As can be imagined, in any of these type of wireless communication systems there are many components that need to be adjusted and tuned so that the system can compensate for frequency shifts and atmospheric disturbances. For example, high or low humidity and temperature, or rain, snow and wind can affect wireless communication systems. Thus, what is needed in the art is a convenient system that detects temperature and/or power levels in the wireless communication transmission and automatically adjusts components within the system to provide for maximum data transmission efficiency.
Furthermore, on the base station side of many radio frequency systems, the gain of the receive (and transmit) path is not completely deterministic and not known in advance due mainly to differing amounts of cable length required to connect the roof-top radio and antenna to the indoor equipment. Like the transmit path, the receive path must be compensated (calibrated) in some manner to produce a known signal level at various points in the receive chain for optimal performance of the system. This compensation or path calibration is ordinarily done by sending a known signal level into the path and adjusting the gain(s) along the path until the signal level measured along the path is at the desired level. This obviously requires some sort of signal generator to produce the signal for this calibration process. In the base station, in the transmit direction, the signal generator could be the base station equipment itself. In the receive direction, there is no xe2x80x9cbuilt-inxe2x80x9d signal generator for the calibration.
This problem can be solved in various ways, some of which are by using equipment external to the base station itself, by including a signal generator in the base station receive path hardware, or by using some sort of transmit signal loop-back scheme in the radio. All of these techniques incur some amount of additional expense and/or complexity in the base station design and/or installation. Thus, what is needed is a way to compensate for the differing cable lengths without incurring additional expense and/or complexity in the base station design and/or installation.
Furthermore, the output power stability of the roof-top radio may be directly affected by the gain of the transmitter circuits. The transmit power should be as high as possible to optimize range but not so high as to cause excessive signal distortion. Thus, what is needed is a way to control the transmitter power so as to provide an optimum transmit power to operate at under all conditions and that is not affected by modulation type.
One aspect of the present invention includes a method of automatically calibrating the gain of an indoor unit of a base station having an outdoor unit and a broadband cable connecting the indoor unit and outdoor unit in a wireless communication system having customer sites, the method comprising determining which customer sites are not operating at maximum power; measuring, for a customer site not operating at maximum power, average received power at the outdoor unit; comparing the average received power to a nominal level; and increasing the gain of the indoor unit if the average received power is greater than the nominal level or decreasing the gain of the indoor unit if the average received power is less than the nominal level.
Another aspect of the present invention includes a base station, configured to automatically calibrate a receive path gain, for use in a wireless communication system having customer sites, the base station comprising an outdoor unit configured to receive signals from the customer sites, wherein the signals include power readings from the customer sites; a broadband cable connected to the outdoor unit; and an indoor unit connected to the broadband cable and configured to receive message data from the outdoor unit through the broadband cable, wherein the indoor unit includes a processor configured to determine which customer sites are not operating at maximum power, instruct the outdoor unit to measure, for a customer site not operating at maximum power, average received power at the outdoor unit, compare the average received power to a nominal level, and increase the gain of the indoor unit if the average received power is greater than the nominal level or decrease the gain of the indoor unit if the average received power is less than the nominal level.
Another aspect of the present invention includes a method of automatically calibrating a receive path gain of a base station having an indoor unit, an outdoor unit and a broadband cable connecting the indoor unit and the outdoor unit in a wireless communication system having one or more customer sites, the method comprising wirelessly receiving signals from one or more customer sites; measuring, for a customer site not operating at maximum power, power of the received signal at the outdoor unit; comparing the power of the received signal to a predetermined level; and increasing a receive path gain of the indoor unit if the power of the received signal is greater than the predetermined level or decreasing the receive path gain of the indoor unit if the power of the received signal is less than the predetermined level.
Another aspect of the present invention includes a method of automatically controlling the transmit power of a customer site by a base station having an indoor unit, an outdoor unit and a broadband cable connecting the indoor unit and the outdoor unit in a wireless communication system so as to automatically compensate for losses due to the cable, the method comprising wirelessly receiving a signal from a customer site that has started to transmit the signal, measuring power of the received signal at the indoor unit, comparing the power of the received signal to a predetermined level, requesting the customer site to decrease the transmit power if the power of the received signal is greater than the predetermined level or requesting the customer site to increase the transmit power if the power of the received signal is less than the predetermined level, and providing a maximum power status to the base station if the customer site is operating at maximum power so as to control automatic compensation for losses due to the base station cable.
Another aspect of the present invention includes a base station configured to automatically calibrate a receive path gain in a wireless communication system having customer sites, the base station comprising an outdoor unit wirelessly receiving signals from the customer sites, wherein the signals include power levels of one or more of the customer sites; a broadband cable connected to the outdoor unit; and an indoor unit connected to the broadband cable and receiving message data from the outdoor unit through the broadband cable, wherein the indoor unit includes a processor configured to measure, for a customer site not operating at maximum power, power of the received signal at the outdoor unit, compare the power of the received signal to a predetermined level, and increase a receive path gain of the indoor unit if the power of the received signal is greater than the predetermined level or decrease the receive path gain of the indoor unit if the power of the received signal is less than the predetermined level.
Another aspect of the present invention includes a base station for maintaining transmit peak power at a constant level regardless of modulation type for use in a wireless communication system, the base station comprising an indoor unit having a modem configured to provide an output and to use multiple modulation types within a single time division duplexing frame; an outdoor unit connected to the indoor unit and having a transmit system configured to upconvert the output of the modem, the outdoor unit comprising a wideband detector configured to monitor a transmit system output signal; a sample and hold circuit connected to the wideband detector, the sample and hold circuit having a gate input; a delay circuit receiving a transmit/receive control signal and providing an output to the gate input of the sample and hold circuit; a transmit level adjust circuit configured to provide a predetermined transmit output level; and a comparator configured to compare the predetermined transmit output level with the output of the sample and hold circuit so as to generate an error signal to maintain transmit peak power at a constant level.
Another aspect of the present invention includes a subsystem for maintaining transmit peak power at a constant level regardless of modulation type in an outdoor unit of a wireless communication system, the subsystem comprising a wideband detector configured to monitor a transmit output signal; a sample and hold circuit connected to the wideband detector, the sample and hold circuit having a gate input; a delay circuit providing an output, indicative of a time in the transmit output signal when a known modulation type occurs, to the gate input of the sample and hold circuit; a transmit level adjust circuit configured to provide a predetermined transmit output level; and a comparator configured to compare the predetermined transmit output level with the output of the sample and hold circuit so as to generate an error signal used to maintain transmit peak power at a constant level.
Yet another aspect of the present invention includes a method of maintaining transmit peak power at a constant level regardless of modulation type in an outdoor unit of a time division duplexing wireless communication system, the method comprising providing a control signal at a predetermined time delay after a transition from a receive mode to a transmit mode, measuring the amplitude of a transmit output signal based on the delayed control signal, providing a predetermined transmit output level, comparing the predetermined transmit output level with the amplitude of the transmit output signal, and generating a signal representative of the comparing so as to maintain transmit peak power at a constant level.